1. Field of the Invention
The present invention relates to a controller with a function of monitoring a state of a coolant.
2. Description of the Related Art
A machine such as machine tool is supplied with a soluble or insoluble coolant (cutting fluid) during machining. The coolant is stored in a coolant tank and is supplied to the machine via a coolant supply pump coupled to the coolant tank. Then, the used coolant is removed to the outside of the machine while being attached on a workpiece, flows around the machine within a guard cover, and is returned to the coolant tank via a coolant recovery path to be adjusted in its fluid quality for reuse.
If a machining condition to be set during machining is not adjusted depending on fluid quality of a coolant when the machining is performed by use of the coolant, quality of the machining may be influenced.
As a conventional technique in terms of fluid quality of such a coolant, for example, Japanese Patent Application Laid-Open No. 2010-188480 discloses therein a technique for measuring fluid quality (pH, hardness, or concentration) of a coolant, comparing the measurement result with a preset threshold, and displaying a message or performing machine operation control depending on the comparison result.
Further, as a conventional technique for managing water quality of a fluid, for example, Japanese Patent Application Laid-Open No. 2003-141310 discloses therein a technique for storing detection data of a water quality detection device of a water processing facility in a management server, supplying detection result information via a communication line, and when an abnormality occurs or there is a risk that an abnormality might occur, determining a countermeasure.
When a coolant is reused while being repeatedly adjusted as described above, even if the fluid quality of the coolant grasped by a measurement value measured by a sensor such as concentration (see FIG. 3A) or pH (see FIG. 3B) is the same, as illustrated in FIG. 3A and FIG. 3B, the performance of the coolant may change over time due to influences of viable bacteria and impurities in the non-adjusted remaining coolant, such as an increase in speed (tilt of a line in FIGS. 3A and 3B) at which the coolant deteriorates (concentration or pH deteriorates). For example, in the examples of FIG. 3A and FIG. 3B, the measurement values with the same concentration and pH of the coolant are indicated at times (1), (2), and (3), while the deterioration speed is the lowest at time (1) and the highest at time (3).
In order to cope with the differences in performance of a coolant which cannot be grasped by a measurement value measured by such a sensor, conventionally a worker changes a machining condition based on information on a state and use duration of the coolant or an interval or the number of times of adjustment. However, the determination of deterioration largely depends on the worker's experience and limited workers can make an accurate determination, and there is a problem that even an experienced worker may differently make a determination.